Recovery of ni from ammonia liquors



Aug. 4, 1953 P. J. MCGAULEY 2,647,823

RECOVERY OF N'i FROM AMMONIA LIQUORS Filed June 4, 1949 ATTORNEY Patented Aug. 4, 1795.3

UNITED sTATEs PATENT OFFICE RECOVERY OF Ni FROM AMMONIA LIQUoRs Patrick J. McGauley, Glen Cove, N. Y., assignor to Chemical Construction Corporation, New York, N. Y., a corporation of Delaware Application June v4, 1949, Serial No. 97,227 4 claims'. (o1. vs -10s) handle iron which is present in most ores. Inv

some cases the quality and/or yield of the product is not as high as may be desired. In almost all such procedures the economics of the necessary operations result in relatively high costs.

It is, therefore, the principal Object of th present invention to devise a simple and straightforward production of metallic nickel in which the quality of the product is suiciently high to meet commercial qualifications Without utilizing the undesirable steps found in current operations. Such a process should not be dependent upon any particular type of ore. It should not requireroasting and/or electrical precipitation. It should not require excessively complicated process steps, unusual reagents or extraordinary equipment.

In general, the process requirements of th present invention have been met in a simple straightforward operation. A suitable nickelbearing ore is leached by any suitable method to place the nickel content thereof in solution. The nickel content thereof is isolated by precipitation as a nickel-ammonium doublesalt, the double salt is redissolved, and the nickel content of the solution is converted to a nickel-ammonium complex salt, and the nickel contentof the resultant solution is precipitated as nickel powder by chemical reduction.

While, as noted above, nickel-bearing ores are not too uncommon, an ore in which nickel is the sole or even the predominant metal-bearing constituent is very rare. Accordingly, the treatment of mixed mineral ores will be discussed as illustrative of the application of the present invention. The largest proportion of most ores isusually some gangue diluent. Consequently, the ore is usually treated by some preliminary concentrationsuch as gravity separation and/or froth flotation Vand the like to eliminate the bulk of the 'g'anguav Such procedures' form an art with which the present invention is not concerned. In the instant application, it is assumed that some such operation has been carried out. and it is the resultant concentrate which is to be treated.

In addition to the gangue ciments, most nickel-f bearing concentrates usually contain additional metals, among which are commonly found copper, iron and cobalt. Any of these, including the nickel, may be present as sulfides. usually in some complex form. However, one or more of the metals may be present as an oxidized mineral. cal, a concentrate containing copper, iron, co-

balt and nickel will be used as illustrative in,

this discussion.

In order to more easily understand the iioW of the present invention, reference is made to the accompanying drawing. The latter constitutes a simplied flowsheet showing the major steps with which the present invention is concerned and their relation to the treatment of. the remainder of the liquor obtained by leachof the ore being treated. In acid leachng,the acid is generally sulfuric and ferric sulfate is; often added therewith. Ammoniacal leach liquors often also contain ammonium salts such as the carbonate and complex metal-ammonium The present invention is applicableto an ions. ore being treated by any of such procedures.`

Because the invention is not limited to a particular type of leaching, in the drawing this operation has been designated generically as a leaching system. Actually, the leaching `is ordinarily carried out in some multiple tank system, the exact arrangement of which is not a critical factor in the process of this application. The copper, iron, cobalt-, and nickel-bearing concentrate is fed thereto. in with one or more suitable leaching agents.

These may be any suitable acid or ammoniacalv leaching liquors, used in a known manner as:

was noted above.

The residual barren solids may be passed to` Because the problems involved are typi- It is treated there-f azi/17,828

A leach liquor containing the dissolved metal values is drawn from the leaching system. In

using most types of acid leaching,particularly` where oxidation is employed, there will be a considerable content of dissolvediron. Where Vdissolved iron salts are present', they'rnust beielimrnated from the solution. It was foundthat the'4 iron can be caused to precipitate `from a concentrated ammonium salt solution at 'a suitable pI-I Y while keeping the metal values in solutio'ri-.`

Accordingly, the pH of the pregnant leach liquor is adjustedto about 3 to 4. Because of the oxidation, which is a normal step of average operationup to this point, any dissolved iron will be principally in the ferric condition. At these pHs, it will precipitate and may be filtered out as'oxideor hydroxide and passed to waste. INeutralization maybe carried out in any desired manner. For example, it may be done by the addition? of ammonia to a sulfuric acid leachv li'qu'oror bythe addition of sulfuric acid to, or by oxidation formation of sulfuric acid in situ in, an ammioniac'al leach liquor. Where the problem of ironis'not involved, this step of pH adjustment and the removal of the resultant iron precipitate mayv be` eliminated if so desired. This omission is indicated in the flowsheet by an optional flow.

Further, ini accordance with the work done in developing' the present invention, it was found that at a pI-I oi 'about 4.0 to about 6.4, in a conc'entrated1 solution of ammonium sulfate, the nickel content of the solution can be precipitated quantitatively as a nickel sulfate-ammonium sulfate-double salt. At the same time other metals, i. e., the cobalt and copper in the illustrative case, can' be retained in solution. Accordingly, the

iron-free, metals-bearingV leach liquor is treated` Inoni'um sulfate may be added Thislatter causesV no'particular problem since, as will be brought out below, ammonium sulfate is one of the usual products ofl the overall process of treating the ore concentrate.

The're'sultant slurry of the double salt is filtered to recover the latter. Ordinarily, the presscake Y is-wa'shed. The washings may be either added to the filtrate or, if so desired, optionally returned-to the leaching system. The filtrate and thefdouble salt presscake are separately treated. The vnickelvalues, with which the present invention is-concerned, are contained in the latter.

The filtrate, which in the illustrative case willv contain the copper Vand cobalt Values as well as theammonium sulfate; is sent to a separatory system; The latter, in its specific details, forms no part of the present invention. Accordingly, it has been generically indicated as a separatory system. So far as thevpresent invention is concerned, it is suincient to note that such a Asystem ordinarily produces ve products. In most cases these are: (1) a copper product, usually as copper metal powder; (2) a cobalt product, usually as cobalt metal powder; (3) ammonium sulfate crystals; (4) a copper-bearing mother liquor; and (5) a cobalt-@bearing motheriliquor. These latter two liquors are ordinarily returned to the leaching system. An excellent separatory system for the purposes of the present invention is shown in my. copending application for United States LettersPatent, Serial No. 97,228, led of even date. However, any desirable system may be used so' faras the present application is concerned.

Returning to the principal now of the present application, the nickel-bearing presscake, which is,constitutedprincipally by the double salt, is

y given the following treatment. Initially the doublfsaltis redissolved. To accomplish this, a surncient amonut of water and ammonia is added to convert the nickel tothe nickel-ammoniumv complexsalt, in the illustrative case the sulfate. The resultant solution is ltered and the solid residue, if any, is passed to Waste.

The filtrate and washings which contain the dissolved nickeleainnionium salt is puriiied, if necessary. Forexample, barium or calcium oxide may be added in suiicient amount to precipitate the sulfate content of any ammonium sulfate in the liquor, the precipitated alkaline-earth metal sulfate being ltered out. If so desired, the nickel-ammonium salt, either per se or after conversion to nickel sulfate, may be purified by ciystallization and then be redissolved. In the latter case,-suilicient ammonia` is added to convert the nickeli to a nickel-ammonium complex salt. If, for anyreason, theipurific'ation step is not required, it may be bypassed. Ordinarily, however, since the purity or the nnal metal product is of great importance commercially,` and the best product can be'obtained only from relatively pure solutions, some purification of nickel solution may be desirable as a precaution.

Finally,l the nickel-ammonium solution is treated to precipitate the nickel content thereof. This is accomplished under increased temperature and pressure conditions in the presence of a re'ducinggas such as carbonmonoxide. It should benoted that successful precipitation cannot be accomplished'if thelhydrogen ion concentration of the solution is allowed to increase appreciably. According-to th'e'present invention, it is therefore preferable to precipitate from a nickel-ammonium complex salt solution; Where the latter is impractical `or undesirable, other means should be provided to eliminate the hydrogen ions formed-during reduction. Reduction, i. e., precipitation, is carried out at any convenient temperature and pres'sure, depending upon'the time cycle required. The average-operating conditions will be` found to'liefwithin a temperature range of about 10G-:325 C.,.although higher temperatures may be used if apparatus ofY suic'ient strength is available.

Precipitation is. carried as nearly to comple'- tion' as is consistent with the purity of the metal prei-duct.y The latter, with the exception of oxides,.sh0uld besubstantially pure nickel. Except for a possible small oxide content, it is easily possible to precipitate powdered nickel having a purity of vabout 99.0%, or better, which is well wit-hin commercial requirements. To insure this condition,(precipitation shouldfnot be carried'out beyondthepointi at which the ratio of nickel to any other extraneous.metal*ions approaches a 1:1

ratio. Ordinarily this will not present a serious problem. Substantially all the nickel usually can be precipitated. rEllis is not a source of any loss of nickel since the unprecipitated nickel mother liquor is recycled. Recycling is usually to the leach system but may be to any step prior to the puriiication step.

In crystallizing the nickel double salt it should be noted that the copper and/or cobalt salts must be retained in solution. It may, therefore, be necessary in some cases to take precautions that the cobalt-nickel and copper-nickel ratios do not exceed the limitations at which, for the ammonium sulfate content of the liquor, the cobalt and copper may be retained in solution.

Assigning numerical limitations within which limits the conditions must be maintained is not readily done. At a pI-I above about 6.5 the Ni++ ion becomes a nickel-ammonium complex such as the Ni NH4 X++ ion, where x varies from about 2-6, depending upon the available ammonia. Below a pH of about 4.0 the double salt does not form. In the case of cobalt, the corresponding pH values are about `5.5 and 3.5 respectively. It is necessary for best results that the double salt be precipitated under these conditions.

As to the amount of ammonium sulfate which should be in solution the limits are obviously effected by the temperature. If about 25 C. is taken as illustrative, the nickel double salt is soluble to less than 1% by weight in a solution containing about 9-10% ammonium sulfate and is insoluble in solutions of more than about 20% ammonium sulfate. At these ammonium salt concentrations, the cobalt is soluble from labout 6% down to about 1.5% respectively, and the copper salt from about 10% down to about 2%.

Obviously the solubility of cobalt and copper decreases with increasing ammonium salt concentration. At the same illustrative temperature, cobalt double salt, for example, becomes insoluble at about 40% ammonium salt concentration but copper remains soluble in appreciative amounts to about 50% ammonium salt concentration. Accordingly, it is desirable that the nickel double salt precipitation be carried out at ammonium salt concentrations not much above the minimum at which nickel salt is insoluble. In this way the maximum permissible copper and cobalt concentrations can be maintained. In some cases the cobalt and/or copper to nickel ratios may be higher than the solubility curve will permit the cobalt and copper content to be wholly retained in solution, while the nickel is being precipitated. In such cases the liquor is diluted with respect to the copper and/or cobalt content sufficiently to retain these metals in solution. Dilution will ordinarily be made by recycling barren liquor from which copper and/or cobalt has been removed in the separatory system. If necessary, an ammonium salt concentration adjustment can be made after dilution.

I claim:

1. The treatment of a liquor containing dissolved copper and nickel values to isolate the nickel values which includes the steps of: removing any solids from the liquor; producing in the liquor an ammonium sulfate concentration of from about 10% to about 40%; adjusting the copper content of the liquor to from not more than about 8% at a 10% ammonium sulfate concentration to not more than about 1% at a 40% ammonium sulfate concentration; adjusting the pH of the solids-free liquor to from about 4.0 to about 6.5 whereby all the copper Values remain in solution but substantially all the nickel values are precipitated, and collecting said precipitate.

2. A process according t0 claim 1 in which said liquor contains ferrie ions characterized in that prior to said first removal of solids from the liquor the pI-I thereof is adjusted to from about 3 to about 4 whereby the ferrie iron precipitates, said precipitate being separated from the residual liquor before further pI-I adjustment.

3. The treatment of a liquor containing dissolved cobalt, nickel and copper values to isolate the nickel values which includes the steps of removing any solids from the liquor; producing in the liquor an `ammonium sulfate concentration of from about 10% to about 40%; adjusting the cobait content of the liquor to from not more than about 5% at 10% ammonium sulfate concentration to not more than about 1.5% at a ammonium sulfate concentration and the copper content of the solution to not more than 8 at a 10% ammonium sulfate concentration to not more than about 1% at a 40% ammonium sulfate concentration; adjusting the pH of the solids-free liquor to from about 4 to about 6.5 whereby substantially none of the cobalt and copper values but substantially all of the nickel values are precipitated, and collecting said precipitate.

4. A process according to claim 3, in which said liquor -contains ferrie ions characterized in that prior to the removal of solids from the liquor the l pH thereof is yadjusted to from about 3 to about 4 whereby the ferrie iron precipitates, said precipitate being separated from said residual liquor before further pH adjustment.

PATRICK J. MCGAULEY.

References Cited in the iile of this patent UNITED STATES PATENTS Number Name Date 1,039,861 Wells Oct. 1, 1912 1,686,391 Muller et al. Oct. 2, 1928 2,576,314 Forward Nov. 27, 1951 OTHER REFERENCES Solubilities of Inorganic and Organic Compounds, vol. 2, by Seidell, D. Van Nostrand Co., Inc. (1928), pages 1185 and 1186.

Chemical News, vol. 7 (1863), page 185.

Hydrogen Ions, by Britton, D. Van Nostrand Co., Inc. (1929), page 278. 

1. THE TREATMENT OF A LIQUOR CONTAINING DISSOLVED COPPER AND NICKEL VALUES TO ISOLATE THE NICKEL VALUES WHICH INCLUDES THE STEPS OF: REMOVING ANY SOLIDS FROM THE LIQUOR; PRODUCING IN THE LIQUOR AN AMMONIUM SULFATE CONCENTRATION OF FROM ABOUT 10% TO ABOUT 40%; ADJUSTING THE COPPER CONTENT OF THE LIQUOR TO FROM NOT MORE THAN ABOUT 8% AT A 10% AMMONIUM SULFATE CONCENTRATION TO NOT MORE THAN ABOUT 1% AT A 40% AMMONIUM SULFATE CONCENTRATION; ADJUSTING THE PH OF THE SOLIDS-FREE LIQUOR TO FROM ABOUT 4.0 TO ABOUT 6.5 WHEREBY ALL THE COPPER VALUES REMAIN IN SOLUTION BUT SUBSTANTIALLY ALL THE NICKEL VALUES ARE PRECIPITATED, AND COLLECTING SAID PRECIPITATE.
 2. A PROCESS ACCORDING TO CLAIM 1 IN WHICH SAID LIQUOUR CONTAINS FERRIC IONS CHARACTERIZED IN THAT PRIOR TO SAID FIRST REMOVAL OF SOLIDS FROM THE LIQUOR THE PH THEREOF IS ADJUSTED TO FROM ABOUT 3 TO ABOUT 4 WHEREBY THE FERRIC IRON PRECIPITATES, SAID PRECIPITATES BEING SEPARATED FROM THE RESIDUAL LIQUOR BEFORE FURTHER PH ADJUSTMENT. 